Magnetron device with exiting permanent magnet free from magnetic short-circuiting by frame

ABSTRACT

A MAGNETRON DEVICE IN WHICH AN UPPER INSULATOR VESSEL INCLUDING THEREIN CATHODE LEAD MEMBERS EXTENDING FROM A CATHODE CONTAINED, TOGETHER WITH AN ANODE, A CAVITY RESONATOR AND MAGNETIC POLE PIECES, IN A METAL VESSEL IS DISPOSED IN AN AXIAL HOLE IN A CYLINDRICAL OR CONICAL PERMANENT MAGNET FOR EXCITING A MAGNETRON WITH AN INTERSTICE THEREBETWEEN TO DEFINE A VENTILATION FLUE FOR EFFECTIVELY COOLING THE UPPER INSULATOR VESSEL AND THE PERMANENT MAGNET TO PREVENT THE INSULATOR VESSEL FROM BREAKAGE DUE TO UNEVEN HEATING OF THE INSULATOR VESSEL BY MAKING THE DISTRIBUTION OF THE TEMPERATURE OF THE INSULATOR VESSEL EVEN.

United States Patent inventor Tsuneo Numata Kyoto, Japan Appl. No.833,253

Filed June 16, 1969 Patented June 28, 1971 Assignee MatsushitaElectronics Corporation Osaka, Japan Field olSearch 315/3951, 39.77,39.73, 39.71

References Cited UNITED STATES PATENTS 2/1962 Schall et a1.

Primary Examiner-Herman Karl Saalbach Assistant Examiner-SaxfieldChatmon, Jr. Attorney-Stevens, Davis, Miller & Mosher ABSTRACT: Amagnetron device in which an upper insulator vessel including thereincathode lead members extending from a cathode contained, together withan anode, a cavity resonator and magnetic pole pieces, in a metal vesselis disposed in an axial hole in a cylindrical or conical permanentmagnet for exciting a magnetron with an interstice therebetween todefine a ventilation flue for effectively cooling the upper insulatorvessel and the permanent magnet to prevent the insulator vessel frombreakage due to uneven heating of the insulator vessel by making thedistribution of the temperature of the insulator vessel even.

PAFENIED JUN28 1971 3 588,588

sum 1 [1F 3 INVENTOR TSUNEO NUMATA ATTORNEY PATENTED JUN28 l97l SHEET 2OF 3 PATENIED JUN28 I972 SHEET 3 [1F 3 MAGNETRON DEVICE WITH EXITINGPERMANENT MAGNET FREE FROM MAGNETIC SI-IORT-CIRCUITING BY FRAME Thepresent invention relates to magnetron devices, and more particularly tomagnetron devices suitable for use in electronic ranges.

A magnetron comprising a tubular metal vessel including therein acathode, an anode surrounding said cathode, an upper magnetic polepiece, a lower magnetic pole piece, and a cavity resonator; an upwardlyprojecting upper insulator vessel contiguous to said upper pole pieceand enclosing therein a cathode lead member; and a downwardly projectinglower insulator vessel contiguous to said lower pole piece and enclosingtherein an antennalike electromagnetic wave emitting electrode extendingfrom said cavity resonator is disclosed, for example, in U.S. Pat. No.2,721,294 to E. J. Shelton. A magnetron coupled with a cylindricalpermanent magnet is also known, for example, by U.S. Pat. No. 2,824,261to P. H. Peters et al.

It is an object of the present invention to provide a magnetron devicein which the occupation space of a permanent magnet for exciting amagnetron is made as small as possible so that a compact high frequencyheating apparatus can be provided when the magnetron device is employedtherein.

It is another object of the present invention to provide a magnetrondevice in which an upper insulator vessel is protected by means of apermanent magnet from an impact from outside. I

It is a further object of the present invention to provide a magnetrondevice in which a longitudinal hole in a permanent magnet is employed asa ventilation flue to effectively cool the permanent magnet itself and,at the same time, to make the temperature distribution of an upperinsulator vessel in a longitudinal direction as uniform as possible tothereby protect an upper insulator vessel from breakage due to thermalstrain.

It is a still further object of the present invention to provide amagnetron device in which provision is made against magnetic shortcircuiting of both poles of a permanent magnet.

According to the present invention there is provided a magnetron devicecomprising a magnetron having a tubular metal vessel including therein acathode, an anode surrounding said cathode, an upper magnetic polepiece, a lower magnetic pole piece, and a cavity resonator, an upwardlyprojecting upper insulator vessel contiguous to said upper pole pieceand enclosing a cathode lead member therein, and a downwardly projectinglower insulator vessel contiguous to said lower pole piece and enclosingtherein an antennalike electromagnetic wave emitting electrode extendingfrom said cavity resonator; a permanent magnet having an axial hole thediameter of which is greater than the diameter of said upper insulatorvessel; and yoke means for magnetically coupling said permanent magnetwith said magnetron, characterized in that said permanent magnet isarranged coaxially with said metal vessel in such a manner that at leasta great part of said upper insulator vessel is disposed in said axialhole of said pennanent magnet with interstice therebetween with thelower end surface of said permanent magnet being coupled with the uppersurface of said upper magnetic piece directly or through theintermediary of a yoke member.

Features and advantages of the present invention will become moreapparent from the following detailed description of preferredembodiments of the invention when read with reference to theaccompanying drawings, in which:

FIG. 1 is a partly broken perspective view of an embodiment of theinvention;

FIG. 2 is a partly broken side view of the embodiment of FIG. 1;

FIG. 3 is a partly broken perspective view of another embodiment of theinvention;

FIG. 4 is a partly broken side view of the embodiment of FIG. 3;

FIG. 5 is a partly broken perspective view of a further embodiment ofthe invention;

FIG. 6 is a partly exploded side view of a still further embodiment ofthe invention; and

FIG. 7 is a partly exploded perspective view of another embodiment ofthe invention.

Referring to FIGS. 1 and 2, a magnetron 1 comprises a cylindrical metalvessel 2 and cup-shaped insulator vessels 3 and 4 made of glass, ceramicor the like sealed to the upper and lower ends of the cylindrical metalvessel 2. Inside the metal vessel 2, a cathode 17 and an anode 19surrounding the cathode 17 are provided coaxially with the vessel 2, andupper and lower magnetic pole pieces 24 and 25 are provided at the upperand lower ends of the vessel 2, respectively. Further, in a spaceadjacent to the anode inside the vessel 2 there is provided a cavityresonator 26. Cathode lead members connected with the cathode areenclosed in the upper insulator vessel 3, and an antennalikeelectromagnetic wave emitting electrode 5 extending from the cavityresonator 26 is enclosed in the lower insulator vessel 4.

A radiator 6 for air cooling the magnetron 1 comprises an appropriatenumber of good thermally conductive radiating plates 9 piled up withcertain intervals therebetween disposed between an intake port 7 and anexhaust port 8. The heat radiating plates 9 are welded to thecircumference of 'the metal vessel 2. The radiator 6 effects forcedcooling of the magnetron 1 by combination with a blower.

A conical or cylindrical permanent magnet 10 preferably made of ferritehas an axial hole 11 within which the whole or a great part of the upperinsulator vessel 3 is disposed without touching the magnet 10. The lowerend surface of the permanent magnet 10 is in contact with the uppersurface of the upper pole piece 24 in the metal vessel 2 directly orthrough the intermediary of a thin heat insulating packing, whereby onepole of the pennanent magnet 10 is magnetically coupled with the upperpole piece 24. The other pole, Le. the upper surface of the permanentmagnet 10 is magnetically coupled with the lower pole piece 25 through ahigh permeability metal frame members 12 and 13 which serve as magneticcoupling means, the frame member 13 being in contact with the lowersurface of the lower pole piece 25 directly or through an interposedthin heat insulating packing. The frame member 13 has a hole 14 throughwhich the lower insulator vessel 4 enclosing therein the electromagneticwave emitting electrode 5 protrudes downward. The frame member 13 hasalso an appropriate number of holes 15 for screws for mounting themagnetron device on an electronic range. Leadout parts 16 of the cathodelead members extend outward from the upper insulator vessel 3.

According to the second embodiment of this invention shown in FIGS. 3and 4, the radiator 6 has a second exhaust port 18, and the permanentmagnet 10 has a ventilation flue 20 cut through the sidewall thereof. Inthis case, a cooling air current fed from the intake port 7 of theradiator 6 through the exhaust port 18 to the permanent magnet 10 is ledto the magnetron 1 through the ventilation flue 20, and goes up in theaxial hole 11 along the surface of the heated upper insulator vessel 3to effectively cool the permanent magnet 10 and the upper insulatorvessel 3. Although the ventilation flue 20 is shown as of slit shape inFIGS. 3 and 4, other shapes of hole or channel may be employed as well.Of course, two or more ventilation flues can be employed. It is notalways necessary to supply the cooling air current to the ventilationflue 20 through the radiator 6, but it may be supplied directly from ablower.

When it is difficult to form the ventilation flue 20 through thesidewall of the conical permanent magnet 10, it is possible to provide aconical yoke 21 made of previously magnetized or not previouslymagnetized ferromagnetic material between the permanent magnet 10 andthe upper pole piece and to provide a ventilation flue 22 through thesidewall of the yoke as shown in FIG. 5. An axial hole 23 of the conicalyoke 21 and the axial hole 11 of the cylindrical permanent magnet 10 arecommunicating with each other, and the upper insulator vessel 3 isincluded in the axial holes 11 and 23 without contactupper magnetic polepiece.

Although as the cylindrical or conical permanent magnet having an axialhole both of the so-called barium-ferrite group magnet and the alnicogroup magnet can be employed, the former magnet is preferable to thedevice of this invention for the reason that the ferrite group magnethas a good workability and is excellent in the efficiency of heatabsorption and heat radiation because ofits pitch-dark color. Since thepermanent magnet 10 surrounds the upper insulator vessel 3 almost alongthe entire length ofthe vessel 3, the magnet 10, when it is of ferrite,effectively dissipates the heat of the magnetron 1 generated at the timeof its operation, and makes the heating of the whole of the upperinsulator vessel 3 approximately even to reduce the strain of the vessel3 resulting from uneven heating. It is desirable to provide amagnetoshielding metal layer on the surface of the wall of the axialhole of the ferrite magnet 10.

In the embodiments of the present invention so far described, when theperiphery of particularly the lower edge of the permanent magnet 10 andthe metal frame member R2 are close to each other, both poles of thepermanent magnet 10 are substantially magnetically short circuitedthrough the frame member 12 with the result that the density of magneticflux to be supplied to the magnetron l is reduced. An embodimentprovided against this short circuiting is shown in FIG. 6.

In FIG. 6, magnets 30 for repulsion are provided on the inner side ofthe frame member 12 at positions corresponding to the lower pole of thepermanent magnet 10 in such a manner that the lower pole of thepermanent magnet 10 and the same kind of poles of the magnets 30 areopposed to each other. Consequently, the short circuiting of thepermanent magnet 10 by means of the frame member 12 is prevented by themagnetic field originated from the magnets 30. It was found byexperiments that while the density of magnetic flux supplied to themetal vessel 2 was about 1,730 gauss when the outer diameter of themetal vessel 2 was 70 mm., the outer diameter and height of thecylindrical permanent magnet 10 were about 80 mm. and 45 mm.,respectively, and the interval between the outer wall of the permanentmagnet 10 and the inner wall of the frame member 112 was about mm., itwas increased to about L880 gauss when two small permanent magnets forrepulsive magnetic field generation were employed. Either permanentmagnets or electromagnets can be employed as the magnets 30 for therepulsive field generation.

In the embodiment shown in FIG. 7, a cylindrical permanent magnet 100surrounds not only all or a great part of the insulator vessel 3, butalso the metal vessel 2 and the radiator 6. A window'ltll formed throughthe sidewall of the permanent magnet I00 fits the intake port 8 of theradiator 6. A yoke 102 in this embodiment is cylindrical and arrangedinside the cylindrical permanent magnet 100.

lclaim:

l A magnetron device comprising a magnetron having a tubular metalvessel including therein a cathode, an anode surrounding said cathode,an upper magnetic pole piece 24, a lower magnetic pole piece, and acavity resonator, an upwardly projecting upper insulator vesselcontiguous to said upper pole piece and enclosing a cathode lead membertherein, and a downwardly projecting lower insulator vessel contiguousto said lower pole piece and enclosing therein an antennalikeelectromagnetic wave emitting electrode extending from said cavityresonator; a permanent magnet having an axial hole the diameter of whichis greater than the diameter of said upper insulator vessel; and a framemember magnetically coupling said permanent magnet with said magnetron,wherein said permanent magnet is arranged coaxially with said metalvessel in such a manner that at least a greater part of said upperinsulator vessel is disposed in said axial hole of said permanent magnetwith an air space therebetween with the lower end surface of saidpermanent magnet being coupled with the upper surface of said uppermagnetic pole piece, and means preventing said permanent magnet frombeing magneti cally short circuited through said frame member.

2. A magnetron device according to claim 1, wherein said permanentmagnet is provided with at least one hole or channel through itssidewall, said hole'or channel communicating with said air space todefine a ventilation flue.

3. A magnetron device according to claim ll, comprising a yoke memberinterposed between said permanent magnet and said upper magnetic pole,said yoke member being provided with at least one hole or channelthrough its sidewall, said hole or channel communicating with said airspace to define a ventilation flue.

4. A magnetron device according to claim I, in which said permanentmagnet is a ferrite group magnet.

5. A magnetron device according to claim I, wherein said frame member isprovided with at least one magnet for developing a repulsive field tosaid permanent magnet at a position close to and opposing the peripheryof the lower edge ofsaid permanent magnet.

6. A magnetron device according to claim 4, wherein the sidewall of saidaxial hole of said permanent magnet is provided with a magnetoshieldingmetal layer.

7. A magnetron device comprising a magnetron having a tubular metalvessel including therein a cathode, an anode surrounding said cathode,an upper magnetic pole piece, a lower magnetic pole piece, and a cavityresonator, an upwardly projecting upper insulator vessel contiguous tosaid upper pole piece and enclosing a cathode lead member therein, and adownwardly projecting lower insulator vessel contiguous to said lowerpole piece and enclosing therein an antennalike electromagnetic waveemitting electrode extending from said cavity resonator; a permanentmagnet having an axial hole the diameter of which is greater than thediameter of said upper insulator vessel; and yoke means for magneticallycoupling said permanent magnet with said magnetron, wherein saidpermanent magnet is arranged on said upper magnetic pole piece such thatsaid upper insulator vessel is disposed in said axial hole of saidpermanent magnet with an air space therebetween defining a ventilationflue, and said lower insulator vessel extends downward through said yokemeans.

8. A magnetron device according to claim ll, wherein the lower diameterof said permanent magnet is smaller than the upper diameter thereof.

9. A magnetron device according to claim I, wherein the lateralextension of the lower part of said frame member is larger than that ofthe upper part thereof.

10. A magnetron device according to claim 3, wherein the lower diameterof said yoke member is smaller than the upper diameter thereof. I

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 588 D td June 28, 1971 Inventor) Tsuneo NUMATA It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

The Claim for Convention Priority and six Japanese patent applicationsshould be listed as follows:

Patent Appln. Patent Appln. Patent Appln. Patent Appln. Utility ModelUtility Model Japan, Japan, Japan, Japan, Japan, Japan,

Signed and sealed this 25th day of January 1972.

SEAL) attest:

ROBERT GOTTSCHALK EDWARD M.FLETCHER, JR. Commissioner of Patents eatingOfficer and FORM O-1050110459? USCOMM-DC 60376-P59 W U 5 GOVERNMENYPRINTING OFFICE I969 0-366-33l

